292 
Journal of Agricultural Research 
Vol. II, No. 4 
THE YUMA VARIETY 
As compared with the parent Mit Afifi, the Yuma variety is readily 
distinguished by its more frequently 5-lobed leaves (PI. XIX); larger 
involucral bracts (PI. XXII, fig. 2), which tend to be oblong-ovate 
rather than triangular-ovate and are usually united near the base so as 
to foriii a closed cup around the base of the boll; much longer and more 
tapering bolls (PI. XXIV, fig. 2); and longer, lighter colored fiber. The 
fiber averages about 1 % inches long and resembles in color that of the 
Egyptian Yannovitch. In the characters of the foliage, involucres, and 
bolls the Yuma variety shows a striking resemblance to the Egyptian 
Nubari (PI. XXII, fig. 1, and PI. XXIV, fig. 1) which had appeared in 
Egypt three or four years earlier, presumably also by mutation from 
the Mit Afifi. 1 The fiber of the two varieties is quite different, however, 
that of the Yuma being longer and lighter colored. 
The Yuma variety showed from the beginning a high degree of uniform¬ 
ity. In 1909 a 4-acre field was grown near Yuma, Ariz., having been 
planted with seed from those plants in the progeny row of 1908 which 
were not individually selected. Every plant in this field was examined 
in June, when 2 per cent of the total number were removed because they 
showed signs of hybrid origin or were otherwise undesirable. A second 
census in July resulted in the removal of an additional 0.5 per cent of the 
plants. The fact that not more than 2.5 per cent of the plants in this 
field showed a noteworthy departure from the type indicates a strong 
predominance of self-pollination or else a high degree of prepotency, since 
the progeny row of 1908 was situated between two rows of plants of 
wholly different character and since in 1906 and 1907 the stock from 
which this mutant came had been exposed to cross-pollination by 
Upland varieties of cotton. 2 
In 1913 Messrs. G. B. Gilbert and M. W. Buster, of the Office of 
Acclimatization and Adaptation of Crop Plants and Cotton Breeding, 
Bureau of Plant Industry, examined all the plants in two fields of the 
Yuma variety at Mesa, Ariz. Although these fields aggregated about 
50 acres in extent and contained several hundred thousand plants, only 
about one dozen individuals were discovered which gave clear evidence 
of contamination with Hindi or with Upland cotton. 
THE PIMA VARIETY 
The Pima variety originated in 1910 with a single plant of marked indi¬ 
viduality which was found growing in a field of the Yuma variety. 
During the three subsequent generations this type has shown a striking 
1 Since the Hit Afifi seed with which the breeding work was begun in Arizona was imported in 1901, two 
years before the appearance of the parent individual of the Nubari variety; and since the latter is too dis¬ 
tinct from Hit Afifi to be overlooked in progeny rows in which every individual plant was closely inspected, 
the possibility of a direct descent of the Yuma from the Nubari seems definitely excluded. 
2 Careful examination of all the plants in the Egyptian cotton progeny rows in 1908 showed that 8.1 per 
cent of the total number were Egyptian X Upland hybrids. In the Yuma variety row 7 plants out of 162, 
or about 4 per cent of the total number of individuals, were hybrids. 
